design and installation of solar power
- Solar Water Heating
- How Solar Heating Works
- Why Solar Heating
- Solar Heating For Swimming Pools
Solar Water Heating
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Domestic Water Heating Domestic water heating is perhaps the best overall potential application for active solar heating in the UK and accounts for approximately 6% of the total national delivered energy use. Domestic water heating demand continues all the year round and still needs to be satisfied in the summer when there is plenty of solar energy available. Incoming mains water is usually at a temperature of around 10 degrees Celsius in the UK and has to be heated, under recent recommendations, to a storage temperature of at least 60 degrees Celsius. For water heating, a typical UK house uses 5kWh per day of useful energy (that is the energy content of the water leaving the taps). This figure can vary considerably from house to house, dependent on household size and water usage. The actual amount of delivered energy (the energy registered on a gas or electricity meter) can be considerably higher, particularly in summer. Running a boiler with a continuously burning pilot light and uninsulated hot water pipe runs for small quantities of hot water reduces efficiency considerably. Even electric immersion heaters may only manage 50% efficiency in terms of useful energy at the tap, boilers considerably less. We could try to design a water heating system to give as close as possible to 100% of the daily requirements in winter. It would, however, be at an unacceptable cost relative to the financial returns and would give us too much hot water in the summer. Hence, solar water heating systems for domestic hot water are usually designed to achieve almost all of summer requirements, and will use a backup heat source to provide the short fall over the rest of the year. A well designed system will typically provide 80% of a family's hot water requirements during the summer months of April to September and make a useful contribution during the rest of the year. In a typical year the system will overall provide 30-70% of a family's annual domestic water heating needs. This percentage is sometimes referred to as the solar fraction.
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Water Heating for Agricultural and Commercial Purposes Agricultural and commercial systems have not received much attention in the UK in terms of solar water heating. Dairies, hotels, sheltered housing, etc., use considerable quantities of hot water, which make them good candidates for solar systems. In broad terms, such systems are only larger versions of domestic systems. In addition, non-profit organisations are entitled to a grant of up to 50% of the installation costs from Phase 2 of the Low Carbon Buildings Programme, if installed by an accredited solar company.
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How Solar Works
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| The idea behind technologies that use solar energy is to harness the freely available rays from the sun in a useful way. The technologies used for solar water heating are simple and effective. The basic principal uses an absorber plate, which is heated by the Sun's rays. The heat is collected in a transfer liquid, which is in turn used in a heat exchanger to heat water. There are many designs of solar water heating and all work well within their design limits. Here at Bright Energy we believe the system that works best in the UK is an indirect system using a twin coil hot water cylinder) coupled with evacuated tubes. Please see the diagram above. |
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Why Solar Heating
A few years ago some scientists reported an increase in the so called greenhouse gases carbon dioxide and methane in the Earth's atmosphere. They predicted that this would result in major changes in the climate. The increase in greenhouse gas levels was attributed to the increasing demand for energy and the resultant increase of fossil fuels.
Although the existence of global warming caused by greenhouse gases has been subject to some dispute, it is now generally acknowledged to be a real phenomenon. Changes in weather patterns are seen as part of a real trend and not simply variations within the normal historical pattern. And with the release of the Stern Report of 2006, this prediction is becoming widely accepted.
Climate change conferences involving governments have been held at Rio and Kyoto resulting in Agenda 21, a commitment by states to achieve a more sustainable pattern of development for this century. The UK is committed to reduce carbon dioxide emissions by 20% by the year 2010. But these targets are likely to be just the beginning of a new focus on measures to slow down climate change. In 2002, the Royal Commission on Environmental Pollution recommended to the UK Government that the UK should aim to reduce emissions of carbon dioxide by 60% by 2050. There is likely to be a huge increase in the use of renewable energy technologies in the UK in order to work towards this sort of target.
The increase in oil prices intensifies the focus on efforts to stimulate the use of renewable energy.
The Environmental Argument
One of the biggest advantages that solar water heating has is its ability to reduce the use of fossil fuels and thereby to help limit the emissions of harmful greenhouse gases.
A well designed solar water heating system installed in a family house which previously used an electric immersion heater to heat water can save in excess of half a tonne of carbon dioxide emissions per annum.
If installed on a large scale, therefore, solar water heating could on its own make a major contribution toward the UK reducing greenhouse gas emissions.
For the general public, solar water heating is the most practicable and effective way in which they can use and enjoy renewable energy in their own homes. People with solar systems in their houses can literally see (in those cases where there is a digital read-out on their system controller) and feel (in hot water) the benefits of the technology. Market research confirms that those householders who over the years have invested in solar water heating systems are very happy with their systems, which they find to be reliable and to make a major contribution to their water heating energy needs.
Solar Heating for Swimming Pools
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The heating of swimming pools is one of the best established applications of solar water heating and also one of the most appropriate because of the high system efficiencies that can be obtained. Average collector efficiencies of approximately 75% can be obtained. The heating of indoor swimming pools can be very expensive so the use of solar heating can be very cost effective. However the installation of solar heating for swimming pools is very specialised and needs to be undertaken by an experienced solar heating company. Here at Bright Energy we have the experience. The installation itself is quite straight forward with the solar array heating indirectly a stainless steel heat exchanger which is placed after the pool filtration unit and before any other heat source such as a boiler. The problems come with the balancing of the system. Since you are dealing with quite a number of solar panels which are usually arranged in banks, the flow between these panels is critical to the correct working of the system. |
Another area of concern is the placing of the heat exchanger. This is normally placed in the plastic pipe work of the pool filtration unit. Care must be taken so that the system does not over heat with the very real possibility of the plastic pipes melting. It is also very important to size the expansion vessels correctly and also to have some protection for the expansion vessels. If you are interested in solar heating for your pool then please contact us to discuss your requirements.  |